1. Field of the Invention
This invention relates to pneumatic tires and more particularly to a safety pneumatic tire for motorcycles which is often used with its rotary shaft inclined at a relatively large angle with respect to the road surface and which can run under its punctured condition.
2. Description of the Prior Art
In recent years paved roads and highways are becoming completed and running performance of vehicles are becoming ever improved. As a result, the vehicles tend to run at a high speed and hence a more effective driver protection means is now urgently in demand.
Recently, tires are not often punctured by penetrations of obstacles such as a nail therethrough because of paved roads. Existing traffic congestion and high speeds of vehicles have become remarkable beyond comparison with the past. Under such circumstances, if tires while running become punctured and vehicles could not run further, the drive is inconvenienced. Particularly, if a tire for motorcycles (hereinafter is called as two-wheeled vehicles,) in high speed running becomes punctured, there is the danger of the motorcycle falling down.
Various types of pneumatic tires comprising an inner tire or means for enabling the tire to run in a safety state even after the puncture of tire have heretofore been proposed. Among these tires, a so-called sidewall reinforcing type tire comprising a hard rubber layer extending from the sidewall of the tire to the tread and supporting the load subjected to the tire by inherent rigidity of the sidewall when it is punctured is particularly usefull as a tire for two-wheeled vehicles.
Such type of tire has a high load supporting ability, but when a rear wheel of the two-wheeled vehicle becomes punctured, if the wheels are inclined to the road surface of the purpose of cornering, that is, if the equational plane of the tire is inclined at an angle with respect to a perpendicular plane to the road (hereinafter called camber angle) and if the camber angle exceeds a given angle, the centrifugal force acting in a direction in parallel with the road surface causes the tire to suddenly bend. As a result, the rear wheel slips in a direction opposite to the cornering direction and hence the front portion of the vehicle tends to turn toward the cornering direction by an extent exceeding that aimed at by the driver, thereby involving an excessively large oversteering. Average drivers could not deal with such phenomenon and hence there is a risk of the vehicle falling and the drivers injured.
This problem is much worth consideration since the driver could not be aware of the abnormal state of the tire due to its puncture when the above mentioned tire having a high load supporting ability is running straight ahead on road.